Oxidized polyisobutylene



Patented Feb. 15, 1949 OXIDIZED POLYISOBUTYLENE Garland H. B. Davis,Elizabeth, N. J., assignor to Standard Oil Development Company, acorporation of Delaware No Drawing. Application September 16, 1944,Serial No. 554,542

3 Claims.

The present invention relates to improved polymeric materials, relatesparticularly to linear chain oleflnic polymers; and relates especiallyto means for converting linear hydrocarbon polymers into oxygenatedsubstances which are soluble in oxygenated solvents, remain soluble inhydrocarbon solvents and, in addition, are compatible withoxygen-containing materials such as res-V ins, cellulosic derivatives,and the like.

This application is a continuation-in-part of my prior filed applicationSerial No. 234,965, filed October 14, 1938, now abandoned.

Linear hydrocarbon polymers, such as the polymers of iso-olefins and, inparticular, polyisobutylene and polyisoamylene, are well known.Likewise, polymers of ethylene and propylene made under high pressurewith small amounts of oxygen; hydrogenated polymerized di-olefins,particularly butadiene or isoprene, are other examples of materials ofthis type. These various materials are purely hydrocarbon and areextremely useful as thickening agents for lubricating oils, particularlywhen they reach molecular weights in excess of 800 or 1,000, as Well asfor other purposes. They can be produced with molecular weightsconsiderably higher, for example, 15,000 to 20,000, 50,000, 100,000 oreven 250,000, but the applicability of these products to variousindustrial uses is limited to some extent because of their lack ofsolubility in oxygen-containing solvents, such as the lower alcohols,ketones, acids, esters, ethers and the like, and their incompatibilitywith oxygen-containing resins as well as with cellulose derivatives suchas the acetates and the others. It is desirable to modify thehydrocarbon polymers so as to make them soluble in oxygen-containingsolvents and compatible with oxygen-containing resins, while preservingtheir valuable physical properties, and hydrocarbon solubility.

It has been found that this can be done by first preparing thehydrocarbon polymers which have been described above and then submittingthe same to an oxidation treatment so as to inporate a certain amount ofoxygen. One of the 2 by molecular oxygen and ordinary oxygen-containingsubstances.

features of the hydrocarbon polymers is their substantially saturatednature, as indicated by low iodine and bromine numbers, but it has beenfound that they may be oxidized by the use of certain oxidation agents.particularly what may be termed chemical oxidizing agents such as nitricacid, nitric oxides and ozone, as well as by means of dichromates,permanganates and the like. It is characteristic of these oxidationagents that they liberate nascent or atomic oxygen which is required forthe oxidation reaction, since The polymers preferably are first broughtinto solution in a suitable solvent, preferably asaturated aliphatichydrocarbon such as naphtha, kerosene or the like, or in a non-reactivehalogenated solvent such as carbon tetrachloride, and this solution isthen a itated with or treated with the chemical oxidizing agent at anelevated temperature, or if desired the solution may be passed through aheated tube with the oxidizing agent. As stated above, the polymers areresistant to oxidation, especially with air, and the conditions ofoxidation with these various oxidizing agents are necessarily severe,depending to some extent on the extent of oxygen incorporation desired.The temperature, time and the amount of the oxidizing agent may bevaried and in this way various amounts of oxygen may be introduced up to30% or 35%, or more, but generally speaking, considerably less oxidationwill effect solubility in the more common oxygen-containing solvents.The time of reaction necessarily depends on other factors and may becompensated for by adjustment of these other factors, but in general anhour or more up to as much as or hours is recommended. In some instancesas much as four to ten hours are suitable. The temperature depends onthe strength or concentration of the oxidizing agent, but generallytemperatures of about 212 F. are required but they should not be allowedto go over about 250 F. so as to prevent too extensive depolymerization.

When using nitric acid as the oxidizing agent, commercial concentratedacid of 1.42 gravity may be used successfully but weaker acids aresometimes useful. It is desirable also to use mixtures of concentratednitric and sulphuric acid but the amount of sulphuric acid should not betoo large because it has a marked tendency to cause depolymerization. Itis desirable to have less than 30% to 50% of sulphuric acid in themixture. It is also found that the higher the molecular weight of theinitial polymer, the more easily it is degraded or depolymerized, sothat when it is desired to maintain the highest possible molecularweight, it is preferred to omit sulphuric acid.

It may be noted that the molecular weight of the oxidized polymer is afunction both of the molecular weight of the starting material and ofthe severity of the oxidation treatment correlated with the amount ofthe oxygen combined into the polymer. The oxidation treatment alwaysyields some molecular weight reduction, and the more severe thetreatment, the greater the breakdown. Thus, if the starting polymer hasa. molecular weight in the neighborhood of 250,000

the p ymers are fully esistant to o y im to or above, and the oxidationtreatment is conducted at a minimum temperature with a minimum amount ofadded oxygen, say 1 or 2%, the molecular weight may be reduced by notmore than .5 or 10%, yielding an oxidized polymer containa molecularweight of 225,000 or above, by a relatively gentle oxidation treatment.Alternatively, I

by a treatment of a 250,000 molecular weight polymer at a hightemperature, with strong sulphuric acid and a minimum of nitric acid, apolymer having a molecular weight ranging from 12,500 to 4,500 mayreadily be obtained, containing from 2 to 5% of oxygen, or by the use ofrelatively larger quantities of oxidizing agent, such as nitric acid, inthe presence of concentrated sulphuric acid and high temperature, a rawpolymer having a molecular weight of 250,000 or above may be convertedto a polymer having 30% to 35% of oxygen and a molecular weight as lowas 12,500 to 4,500. Alternatively, by proper choice of acidconcentration and temperature, any desired molecular weight between avalue about less than that of the starting material and 4,500 may beobtained, with an oxygen content of any desired value, although a highoxygen content and a low molecular weight breakdown cannot be hadsimultaneously, 'a minimum breakdown requiring also a relatively smallamount of oxygen, although a high breakdown with a minimum amount ofoxygen is readily obtained.

Alternatively, if lower molecular weight starting materials are used,lower molecular weight oxygenated products are necessarily obtained, thesame rule of minimum breakdown with minimum oxygen content being stillapplicable.

As stated before, other oxidizing agents may be used such as potassiumpermanganate or potassium dichromate. Ozone may also be employed, but ofall of these the nitric acid is the preferred oxidizing agent. These arebroadly described as atomic oxidizing agents" to distinguish from air ormolecular oxygen which are unsatisfactory.

The product does not greatly diifer in appearance from the initialmaterial. It remains clear but usually takes on a yellow to brown colordepending upon the severity of the oxidation treatment. The consistencyof the product depends to some extent on the original polymer and alsoon the amount of depolymerization eifected through oxidation. Thus, anoriginal solid polymer having a molecular weight of about 100,000 whichis carefully treated so as to minimize degration may remain solid afteroxidation, while a product of 20,000 to 30,000 original molecular weightwhich is a soft solid, treated under similar conditions would beconverted into a viscous liquid. Th amount of nitrogen introduced duringthe oxidation with nitric acid is quite small: in almost every case,less than .25%. The nature of the chemical group formed by the oxidationis not clear at the present time. A small amount of acid is formedduring the treatment and increases during the oxidation, but the amountof oxygen appearing in the form of carboxyllc groups seems to be lessthan 10% of the total oxygen absorbed.

Acetyl values are low, indicating that hydroxyl groups are not formed toany great extent. Qualitative evidence indicates ,that the oxygen may belargely in the form of carbonyl groups but as yet thereis noquantitative demonstration.

The solubility properties of the oxidized material are of the greatestinterest. The hydrocarbon polymers, as stated before, are not soluble inmost oxygen-containing solvents such as ethyl ether, ethyl alcohol,acetone and other low molecular weight ethers, alcohols and ketones.They are not soluble in acetic and similar acids. Oxidation to a limitedextent, for example, 4 to 6%, is suflicient to make the hydrocarbonpolymers soluble in ethyl ether. About 15% oxygen is suflicient to makethem soluble in amyl acetate and similar ester solvents, while it isnecessary to incorporate 28% to 30% of oxygen in order to make themsoluble in acids and ketones. All of the products are soluble however inpetroleum ether and other hydrocarbon solvents, even after oxidation.

These oxidized polymers are likewise compatible with a great manyoxygen-containing substances with which the hydrocarbon polymer isincompatible. It will be understood that there are many such substanceswhich are insoluble in all solvents, for example, the infusible phenolformaldehyde resins and the present polymers are naturally immisciblewith these materials, but they are miscible with a great many of theoxygenated resins which can be put into solution in the various solventsmentioned above. Among the various resins may be noted the naturalresins such as rosin, ester gums, and oleo resins. More specifically,there may be mentioned colophony and rosin oils. Various syntheticresins may also be admixed with those oxygen-containing polymers andamong these may be mentioned the phenol aldehyde resins, aldehydepolymer resins, keto resins, and their various modified forms.

The oxygenated polymers are compatible with various cellulose esters andother derivatives, such as cellulose nitrates, ethers, acetates,propionates, and are very useful in giving such mixtures softness and adegree of elasticity.

The oxidized polymers are also miscible with the unoxidized material, atleast up to the extent 0! 30 or 40% and these mixtures are likewiseuseful.

The nature of the present products and their methods of manufacture areillustrated by the following examples:

Example I 400 grams of polyisobutylene having molecular weight of 13,000as measured by Staudingers viscosity method were mixed with 600 grams ofan oxidizing agent which consisted of 480 parts by weight of nitric acidand parts by weight of sulphuric acid (20%). This mixture was heated to240 F. at which temperature the mixture boiled or gave the appearance ofboiling. This treatment was continued for 72 hours when the mixture wasdiluted with water and the only product separated from the aqueouslayer. It was thoroughly washed, leaving a very viscous, slightly yellowoily material which had a molecular weight of 12,500 and contained 28%of oxygen but the nitrogen content was less than 25%.

This product was soluble in ethyl ether, ethyl alcohol, amyl acetate andacetic acid. It was also found to be soluble in various hydrocarbonaseaeae solvents. It was relatively stable but if heated to atemperature of 125 C. gradually darkened and finally charred. Theproduct was only slightly acid and had low acetyl value below 5.0. Itwas compatible with nitrocellulose, cellulose ether, as well as withvarious oxygen-containing materials. For example, the oxidized polymerwas found to be miscible in equal proportions with nitrocellulose, withethyl cellulose, with rosin Example V of approximately 1.8 sp. g. Themixture was and the mixture taken up in a solvent composed 7 of 30 partsethyl acetate and 30 parts toluene. This likewise gave a clearhomogeneous film as the solvent was evaporated.

Unoxidized polyisobutylene was not compatible with either nitrocelluloseor ethyl cellulose.

and with candelilla wax but the polymer was not heated on the hot platefor approximately eight miscible alkyd resms or drymg oils hours. Duringthis time the purple color of the Example II permanganate entirelydisappeared, indicating the destruction of the permanganate salt. How-The experiment of Example I was repeated but oxidation was discontinuedafter 2 hours and a ever the brown color of manganese salts first samplewas taken. Oxidation was then mamed' A consldfamble i of gas was lvedand a portion of this gas was bubbled resumed for 16 hours longer and asecond sample 3: 1 h l Th was taken. After further oxidation for '72hours rough P ydmxlde so u e res a third sample was taken These Sampleswere lng precipitation indicated the evolution of carbon dioxide showingthat an oxidation reaction was analyzed and No. 1 was found to contain6.2% 2" oxygen sample and occurring. At the end of eight hours the flasksamples 1 and 2 showed the following analyses: was treated withhydrochloric acid which dissolved the brown manganese salts in part.However, the polymer was badly discolored by manplc {233 ganese salts,and no satisfactory analysis for carbon hydroxide and oxygen could beobtained. 1 None The polymer was soluble in both petroleum 2 naphtha andin various of the ester solvents, showing a change in chemicalcomposition. Solubilities of these samples in various mate- Moreover,the physical properties of the polymer rials are summed up in thefollowing table: 30 were greatly changed since it was markedly morefluid and very much more sticky. sample are as: sea as Example t Anotherportion of polyisobutylene having a molecular weight of 100,000 wasshredded as in smble sduble $11 5521" Example V and a 200 gram portionwas placed g2 Soluble JIiO in a two-liter flask to which there was added2, ,5 400 cc of nitric acid (1.4 sp. g.) and 100 cc of 40 sulphuric acid(approximately 1.7 sp. g.). A Example In reflux condenser was thenattached to the flask and the mixture was heated on the hot plate toPolyisobutylene having a molecular weight of refluxing temperature whichwas maintained for 6,000 to 8,000 was dissolved in carbontetrachlotwenty'hours A sample was then removed and ride to give a 6%solution Ommzed 4r the refluxing continued for 10 hours more. Durduced Pa Y Ozonizel' was Passed thmugh ing the entire refluxing treatment largequantities a solutlon for twenty hours at The solvent of brown oxides ofnitrogen were evolved, showing was removed from the product which wasfound that oxidation was occurring At t end f to contain 15% of oxygenand was similar to the these time intervals, the respective samples werematerials produced by means of nitric acid oxidawashed with water bykneading, then were sepa tionrately dissolved in normal butyl acetate.These Emmple IV solutions were washed with water until all tracesPolyisobutylene was oxidized with nitric acid to of acid w v e normal bty ac ta e a degree suiflcient to incorporate 20% oxygen. s thenvolatilized w y f the P y y 10 parts by weight of nitrocellulose and 10parts heat and the last traces were removed by placing of the oxidizedpolyisobutylene were then disthe samples in a vacuum Oven at C. and 29solved in a mixture of 40 parts of butyl acetate, inches of m y v m f r12 ho r 20 parts ethyl acetate and 40 parts toluene. The The respectivesamples were then analyzed for materials were freely soluble and made ahomonitrogen, carbon, hydrogen, ash and sulfur, and geneous film whenthe solvent was allowed to 60 the amount of oxygen present wasdetermined by evaporate. To 10 parts of ethyl cellulose, 10 difierence.The analytic results obtained were parts of the oxidized polyisobutylenewas added as follows:

Time of Per cent Sample 52:? Peiifient Peibc'ent Per cent PeigfintPei-Scent fggn g 1 concurs. 2.12 75.89 12.33 0.01 trace 0.00 2 30hours.2.54 74.42 11.99 0.03 trace 10.05

The physical properties of the oxidized samples were conspicuouslydifferent from the properties of the original sample. The oxidizedsamples were found to be soft, plastic materials in contrast to theoriginal material which was resilient and rubber-like. The oxidizedsamples showed a 7 remarkable tackiness" which was entirely differentfrom that shown by polybutene of lower molecular weight and the sameconsistency; the samples showing a much greater body and a greatertendency to cling to dry surfaces.

Both samples were found to be readily soluble in oxygenated solventssuch as diisopropyl ether, isopropyl acetate, normal butyl ether, andthe like. They were not soluble in acid nor in ethyl alcohol nor inisopropyl alcohol. They were readily soluble in diisobutylene andsimilar hydrocarbon solvents.

Solutions of these samples were made up in diisobutylene and treatedwith dilute aqueous caustic solution. The polymers reacted, forming acompound with the caustic which precipitated from the hydrocarbonsolution, thereby showing the presence in the polymer of free acidgroups, or possibly aldehyde or ketone groups.

The above examples show the oxidation of isobutylene of variousmolecular weights, polyisobutylene being the preferred starting materialpolymer. However, many other polymers may be used, includingpolyethylene, polypropylene, polyamylene and the like, as well as thelowtemperature interpolymers of isobutylene with a polyolefin such asbutadiene or other polyolefin up to about 12 or 14 carbon atoms permolecule, or polymethyl pentadiene Or the like.

Thus, the invention provides means for combining into an olefinicpolymer, from 1% to 30 or 35% of oxygen while bringing the molecular:vghght down to any desired value above about While there are abovedisclosed but a limited number of embodiments of the invention, it ispossible to provide still other embodiments without departing from theinventive concept herein disclosed, and it is therefore desired thatonly such limitations be imposed upon the appended claims as are statedtherein or required by the prior art,

The invention claimed is:

1. The process of oxidizing a polyisobutylene having a molecular weightwithin the range between 5,000 and 250,000, comprising the steps oftreating the polyisobutylene with a mixture of more than 2 parts nitricacid, having a gravity of 1.4 and 1 part of sulphuric acid having agravity of 1.7 at a temperature of approximately 240 F. for asubstantial time interval to yield an oxidized polymer containing oxygenwithin the range of 1% to 28%, a nitrogen content less than 0.25%,having a molecular weight within the range between 4,500 and 225,000;the polymer being characterized by solubility both in hydrocarbonsolvents and in ethers, alcohols and esters.

2. In the process of oxidizing a high molecular weight, linear, polymerof isobutylene having a molecular weight within the range between 10,000and 250,000 the step of treating the polymer with a mixture of 1 partsulfuric acid having a gravity of 1.7 and 4 parts nitric acid having agravity of 1.4 at a temperature within the range between 200 F. to 250F. to yield a clear, yellow to brown, viscous oxidized polymer having amolecular weight range between 5,000, and 10% less than the molecularweight of the original polymer; and characterized by solubility in ethylether, ethyl alcohol, amyl acetate and acetic acid.

3. In the process of oxidizing a high molecular weight, linear, polymerof isobutylene having a molecular weight within the range between 10,-000 and 250,000, the step of treating the polymer with a mixture of 1part sulfuric acid having a gravity of 1.7 and 4 parts of nitric acid,having a gravity of 1.4 at a temperature within the range between 200 F.to 250 F. to yield a clear, yellow to brown, oxidized, viscous polymerhaving a molecular weight range between 5,000, and 10% less than themolecular weight of the original polymer; and characterized bysolubility in ethyl ether, the said oxidized polymer containing between5% and 35% by weight of combined oxygen and less than 0.25% of combinednitrogen.

GARLAND H. B. DAVIS.

REFERENCES CITED The following references are of record in the file ofthis patent; V

UNITED STATES PATENTS Number Name Date 1,062,828 Hofmann May 27, 19132,092,295 Van Peski Sept. 7, 1937 2,115,306 Hampton Apr. 26, 19382,128,574 Van Peski Aug. 30, 1938 2,334,996 Davis Nov. 23, 1943

